An unsaturated oxygen-containing compound, including an unsaturated aldehyde such as acrolein and methacrolein or an unsaturated carboxylic acid such as acrylic acid and methacrylic acid, is generally produced by the vapor-phase catalytic oxidation of propylene or isobutylene as the starting material in the presence of an oxidation catalyst. Recently however, it has come to be paid attention to the method efficient for producing an unsaturated oxygen-containing compound by using an alkane such as propane or isobutane as the starting material which is cheaper than propylene or isobutylene, and there have been proposed various catalysts to use for the said process. A MoVTe type catalyst has been disclosed by JP Laid-Open No. 279351/1994, JP Laid-Open No. 36311/1998, and JP Laid-Open No. 143244/2000. A MoVSb type catalyst has been disclosed by JP Laid-Open No. 316023/1997, JP Laid-Open No. 045664/1998, JP Laid-Open No. 118491/1998, JP Laid-Open No. 120617/1998, JP Laid-Open No. 137585/1998, JP Laid-Open No. 285637/1999, and JP Laid-Open No. 51693/2000.
The MoVTe type catalyst can give acrylic acid as the final product at a high yield, but is likely to lose the catalytic activity if used at a high temperature. Because the tellurium which is one of the essential components of the said catalyst is easy to be evaporated.
In the manufacturing process of the MoVSb type catalyst, molecular oxygen or hydrogen peroxide is added to increase the acrylic acid yield. However, the disclosed reaction temperature is as high as 380° C. or above, there is a problem that the catalyst does not have a sufficient catalytic activity. Therefore, further improvement in the catalytic activity is needed in view of running cost and catalyst life span.
The various catalysts have been proposed to obtain an unsaturated oxygen-containing compound at a high yield from an alkane. But none of them has reached to a commercially applicable level yet.
The commercially applicable catalyst must attain an appropriate alkane conversion, a good acrylic acid selectivity and finally a sufficient acrylic acid yield. Further, its long term stable performance is needed to be kept.